Without limiting the scope of the invention, its background is described in connection with T Cell Receptor mimics.
The present inventors have previously demonstrated Antibodies as T cell receptor mimics, methods of production and uses for the same. For example, United States Patent Application No. 20090304679, filed by Weidanz teaches a methodology of producing and utilizing antibodies that recognize peptides associated with a tumorigenic or disease state, wherein the peptides are displayed in the context of HLA molecules. These antibodies may be utilized in therapeutic methods of mediating cell lysis.
The inventors have previously taught that Class I major histocompatibility complex (MHC) molecules, designated HLA class I in humans, bind and display peptide antigen ligands upon the cell surface. The peptide antigen ligands presented by the class I MHC molecule are derived from either normal endogenous proteins (“self”) or foreign proteins (“non-self”) introduced into the cell. Non-self proteins may be products of malignant transformation or intracellular pathogens such as viruses. In this manner, class I MHC molecules convey information regarding the internal milieu of a cell to immune effector cells including but not limited to, CD8.sup.+ cytotoxic T lymphocytes (CTLs), which are activated upon interaction with “non-self” peptides, thereby lysing or killing the cell presenting such “non-self” peptides.
Class II MHC molecules, designated HLA class II in humans, also bind and display peptide antigen ligands upon the cell surface. Unlike class I MHC molecules which are expressed on virtually all nucleated cells, class II MHC molecules are normally confined to specialized cells, such as B lymphocytes, macrophages, dendritic cells, and other antigen presenting cells which take up foreign antigens from the extracellular fluid via an endocytic pathway. The peptides they bind and present are derived from extracellular foreign antigens, such as products of bacteria that multiply outside of cells, wherein such products include protein toxins secreted by the bacteria that often have deleterious and even lethal effects on the host (e.g., human). In this manner, class II molecules convey information regarding the fitness of the extracellular space in the vicinity of the cell displaying the class II molecule to immune effector cells, including but not limited to, CD4+ helper T cells, thereby helping to eliminate such pathogens. The extermination of such pathogens is accomplished by both helping B cells make antibodies against microbes, as well as toxins produced by such microbes, and by activating macrophages to destroy ingested microbes.
Class I and class II HLA molecules exhibit extensive polymorphism generated by systematic recombinatorial and point mutation events during cell differentiation and maturation resulting from allelic diversity of the parents; as such, hundreds of different HLA types exist throughout the world's population, resulting in a large immunological diversity. Such extensive HLA diversity throughout the population is the root cause of tissue or organ transplant rejection between individuals as well as of differing individual susceptibility and/or resistance to infectious diseases. HLA molecules also contribute significantly to autoimmunity and cancer.
Class I MHC molecules alert the immune response to disorders within host cells. Peptides which are derived from viral- and tumor-specific proteins within the cell are loaded into the class I molecule's antigen binding groove in the endoplasmic reticulum of the cell and subsequently carried to the cell surface. Once the class I MHC molecule and its loaded peptide ligand are on the cell surface, the class I molecule and its peptide ligand are accessible to cytotoxic T lymphocytes (CTL). CTLs survey the peptides presented by the class I molecule and destroy those cells harboring ligands derived from infectious or neoplastic agents within that cell.
The value of monoclonal antibodies which recognize peptide-MHC complexes has been recognized by others (see for example Reiter, US Publication No. US 2004/0191260 A1, filed Mar. 26, 2003; Andersen et al., US Publication No. US 2002/0150914 A1, filed Sep. 19, 2001; Hoogenboom et al., US Publication No. US 2003/0223994 A1, filed Feb. 20, 2003; and Reiter et al., PCT Publication No. WO 03/068201 A2, filed Feb. 11, 2003). However, these processes employ the use of phage display libraries that do not produce a whole, ready-to-use antibody product. The majority of these antibodies were isolated from bacteriophage libraries as Fab fragments (Cohen et al., 2003; Held et al., 2004; and Chames et al., 2000) and have not been examined for anti-tumor activity since they do not activate innate immune mechanisms (e.g., complement-dependent cytotoxicity [CDC]) or antibody-dependent cellular cytotoxicity (ADCC). Demonstration of anti-tumor activity is critical, as therapeutic mAbs are thought to act through several mechanisms, which engage the innate response, including antibody or complement-mediated phagocytosis by macrophage, CDC and ADCC (Liu et al., 2004; Prang et al., 2005; Akewanlop et al., 2001; Clynes et al., 2000; and Masui et al., 1986). These prior art methods also have not demonstrated production of antibodies capable of staining tumor cells in a robust manner, implying that they are of low affinity or specificity. The immunogen employed in the prior art methods uses MHC which has been “enriched” for one particular peptide, and therefore such immunogen contains a pool of peptide-MHC complexes and is not loaded solely with the peptide of interest. In addition, there has not been a concerted effort in these prior art methods to maintain the structure of the three dimensional epitope formed by the peptide/HLA complex, which is essential for generation of the appropriate antibody response. For these reasons, immunization protocols presented in these prior art references had to be carried out over long periods of time (i.e., approximately 5 months or longer).
In addition, the vast majority of phage-derived antibodies produced by the prior art methods will not fold right in mammalian cells due to their selection for expression in prokaryotic or simple eukaryotic systems; generally, <1% of phage-derived antibodies will efficiently fold in mammalian cells, thus greatly increasing the number of candidates that must be screened and virtually assuring that interesting lead candidates with the most desirable binding properties are non-producible in mammalian cells due to the infrequency of success. Supporting this contention is the fact that very few phage-derived antibodies have proceeded into clinical investigation, and no phage-derived antibody has been approved for use as a therapeutic. All approved therapeutic antibodies have their discovery origin from a mammalian species.
Thus, the prior art phage-derived antibodies are not useful for making anti-MHC/peptide complexes, as they typically exhibit low affinity, low robustness, low capability to grow and fold, and as they are generally laborious to implement and have not been shown to be viable for approved therapeutic use.